Discriminatory diagnostic criteria for contourites with respect to other deepwater sedimentary facies

• Main Authors: Hernández-Molina, Francisco J., Rodríguez-Tovar, Francisco Javier, Hüneke, Heiko, Cauxeiro, C., De Castro, S., Rodrigues, S., Glazkova, T., Fonnesu, M., Eggenhuisen, Joris T., Rotzien, J. R., Postma, G., Kleverlaan, K.
• Format: Conference Object
• Language: unknown
• Published: University of Edinburgh 2023
• Subjects: Antarc*; Antarctica
• Online Access: http://hdl.handle.net/10261/353022

Bottom currents and a series of secondary oceanographic processes interact frequently at different scales to form distinct sedimentary deposits referred to as contourite and mixed (turbidite-contourite) depositional systems. These systems represent major depositional systems along the continental margins and abyssal plains of the world¿s oceans. A recent proliferation of both academic and industry research on deep-water sedimentation has revealed significant advances in the understanding of these systems, but non-specialists remain unaware of their sedimentary features and how they were formed. A paucity of examples in the ancient record and a lack of consensus regarding the diagnostic criteria used to characterise and differentiate them from other deep-water deposits limits our understanding of how they may record past processes, such as global oceanic circulation, tectonic events, gateway evolution, among others. In this work, examples of deep-marine deposits from onshore (Cyprus, Morocco, Spain, Italy and Angola) and offshore (Gulf of Cadiz, West Portugal, Mozambique, Antarctica, etc.) areas have been studied through a multidisciplinary approach to discriminate the main deep-water facies as contourites, pelagites/hemipelagites, turbidites, reworked turbidites and mass-transport deposits and determine why, when and how these deposits were formed in response to long-term tectonic history. The results described here highlight the importance of using primary sedimentary structures, microfacies and ichnological features as the best diagnostic criteria to distinguish reworked turbidites from contourites at the sedimentary facies scale. Diagnostic criteria for discriminating bottom current deposits include sedimentary condensation, reworking, reactivation surfaces, smaller grain-size variations, small-scale hiatuses, and omission surfaces. All of these vary according to the paleoenvironmental conditions, especially current velocities and sedimentation rates. Petrophysical properties of such deposits can furthermore ...